A more elgant way to roll up multiple rows? - codeigniter

Question

I'm new to codeigniter (although I suppose this isn't an exclusively CI question) and have a method in a model which selects data from two tables joined by id.
table 1 (tblclients) looks like this:
+----+------------+
+ id + c_name +
+----+------------+
+ 1 + Joe Bloggs +
+ 2 + Jim Bloggs +
+ 3 + Tim Bloggs +
+----+------------+
table 2 (tblstars) looks like this:
+----+------------+
+ id + s_date +
+----+------------+
+ 1 + 27/01/12 +
+ 1 + 15/02/12 +
+ 1 + 18/02/12 +
+ 2 + 03/01/12 +
+ 2 + 11/02/12 +
+ 2 + 15/02/12 +
+ 3 + 01/01/12 +
+ 3 + 19/02/12 +
+----+------------+
I want to 'roll up' the joined data into one line for each row in tblclients so I can output, for example:
+----+------------+--------------------------------+
+ id + Name + Dates +
+----+------------+--------------------------------+
+ 1 + Joe Bloggs + 27/01/12 15/02/12 18/02/12 +
+ 2 + Jim Bloggs + 03/01/12 11/02/12 15/02/12 +
+ 3 + Tim Bloggs + 01/01/12 19/02/12 +
+----+------------+--------------------------------+
Now I've 'solved' the problem by using the following in my model:
function get_clients_concat()
{
$query = $this->db
->select('tblclients.id, tblclients.c_name, GROUP_CONCAT(tblstars.s_date SEPARATOR "#") AS star_dates', NULL, FALSE)
->join('tblstars', 'tblstars.id = tblclients.id', 'left')
->order_by('tblclients.id')
->group_by('tblclients.id')
->get('tblclients');
return $query->result();
}
and then exploding the array (created by the GROUP_CONCAT) in my view and doing some processing with it there ... but it seems really CLUNKY.
Is there a better solution?

Answer 1

If you want to get all that data in a single query (with each row's id unique), then yes--that's the way to go.
If you need to sort or filter the results, you'll run into performance bottlenecks when the tables fill up.
It seems odd though--why wouldn't you select from tblstars (joining tblclients) instead, then use application logic to index the dates by c_name/id?
<?php
// Select data from tables
$data = $this->db
->select('tblclients.id, tblclients.c_name, tblstars.s_date')
->join('tblclients', 'tblclients.id = tblstars.id')
->order_by('tblstars.id')
->get('tblstars');
// Index data by client id
// (keeping record of client name and dates array for each)
$clients = array();
foreach ($data->result() as $result)
{
if (empty($clients[$result->id]))
{
$clients[$result->id] = array(
'name' => $result->c_name,
'dates' => array($result->s_date)
);
}
else
{
$clients[$result->id]['dates'][] = $result->s_date;
}
}
return $clients;